Method of producing wrought structure



Sept. 12, 1967 J, K 3,340,716

METHOD OF PRODUCING WROUGHT STRUCTURE Filed Nov. 10, 1964 T CA5 T moss- ECTION .L HOMOGENIZE 35 5. LLED VIIIIIIIIIIIIIIIIIIA' 1T6" ATE INVEN TOR DONALD J. FUNK ATTORNEYS United States Patent 3,340,716 METHOD OF PRODUCING WROUGHT STRUCTURE Donald J. Funk, Ravenswood, W. Va., assignor to Reynolds Metals Company, Richmond, Va., a corporation of Delaware Filed Nov. 10,- 1964, Ser. No. 410,212 Claims. (Cl. 72-364) ABSTRACT OF THE DISCLOSURE Method of producing Wrought aluminum alloy plate from an homogenized ingot, including the step of hot forging the ingot to effect a reduction of at least 25% in its width dimension, thus forming a rolling billet already worked substantially in a direction corresponding to the short transverse dimension of the resultant plate.

This invention relates to a novel method for the manufacture of wrought aluminum alloy structures of large size. More particularly, the invention concerns a method of producing heavy aluminum plate products and the like by a particular sequence of forging and rolling steps.

The production of wrought aluminum alloy structures, such as, for example, a plate, having a thickness of 3 inches or more, and having a width of several feet and a length of 35 to 50 feet, has heretofore presented considerable difliculties. A sound wrought structure of substantial thickness requires an amount of Working such that the orginal cast slab or ingot from which it is to be made would have to be much too large for practical purposes, a reduction in thickness in the order of 90% being required. If a 5-inch thick plate were desired, therefore, the ingot thickness might be expected to exceed 4 feet. Such an ingot could not be handled in ordinary rolling mills, and, indeed, even were a special mill to be provided for the purpose, it is unlikely that such a rolling operation would be effective to produce a plate having suitable physical properties, because the reduction of such a large ingot by rolling alone could not be relied upon to produce a wrought structure extending throughout the metal.

Another problem associated with rolling plate having a thickness upwards of about 3 inches concerns the necessity of developing sufiicient short transverse strength and adequate elongation, since rolling of a cast ingot to the requisite heavy reductions produces disproportionate working of the cast structure in the long transverse direction of the plate. In accordance with the invention, however, it has been found that wrought aluminum alloy structures of large dimensions can be produced successfully by first subjecting an ingot of reasonable size to a preforging operation, under controlled conditions, to provide a forged billet especially adapted for subsequent rolling. An advantage of the preforging step employed in the practice of the invention is that preliminary working of the ingot may be accomplished which is orthogonally Oriented to the direction of the principal working effect of the subsequent rolling operation. This results in more uniform working of the cast structure.

According to the method of the invention, the forging operation is advantageously applied to a substantially rectangular ingot which is considerably wider in crosssection than its thickness and has a length suflicient to produce the desired length of product. The ingot is placed on its side and forged in such manner that its width is subjected to a substantial reduction under conditions Which produce no significant long transverse working (i.e. by allowing expansion of the length and thickness of the ingot) and which effect a forging reduction greater than 25 in a direction corresponding to the short transverse direction of the resultant plate. This preforging step is followed by a rolling operation which further reduces the forged dimension by a minimum reduction of about 3: 1. Such a combination of forging and rolling operations has been found to develop satisfactory wrought properties in the rolled plate, including short transverse strength and elongation unattainable in thick plates produced by rolling alone.

Other objects, advantages and details will be apparent from the following examples with reference to the drawings, in which:

FIG. 1 shows an ingot;

FIG. 2 indicates schematically the sequence of operations in accordance with the invention;

FIG. 3 illustrates the stages of forming the ingot into a rolled plate.

The practice of the present invention is illustrated by the following examples:

Example 1 Aluminum alloy 2219 was cast to form an ingot measuring 26 x 72 inches in cross-section, about 15 to 20 feet in length, and thereafter given an homogenization treatment at 900-1000 F. for about 48 hours. Opposite faces of the ingot were scalped (reducing the 26" thickness to about 24"), and a section was sawed from the scalped ingot to provide a 24 x 72 x inch forging billet.

During a subsequent hot forging operation the 72" width of the billet was reduced by about 76% to approximately 17 inches, which resulted in the 24 inch dimen sion being increased about 50%.

The forged billet was scalped to a thickness of about 16 inches, heated to about 940 F. and rolled into a 5- inch plate, the rolling reduction consequently being about 65%. The plate was heat treated and aged in conventional manner. Typical mechanical properties of the plate are summarized in Table I.

Example 2 For comparison purposes, the procedure set forth in Example 1 was followed with another 26 x 72 inch ingot, except that the billet was rotated about its longitudinal axis following an initial forging reduction of about 50% (at which stage the partially forged billet measured approximately 33 x 33 inches in cross-section). Then the billet was subjected to an additional forging operation to reduce its thickness (originally the 26" dimension to about 16 inches, thus providing another 50% reduction in a direction orthogonal to the first forging reduction. Plate of 5 inch thickness rolled from this billet, by further reducing the 16" dimension, exhibiting metallurgical structure very similar to that produced in the preceding example.

Example 3 Additional forging and rolling operations were performed in substantially the same manner as detailed in Example 1, except that the cast ingot of 2219 alloy was step-forged to provide different reductions along its length. After rolling into 5-inch plate, it was found that comparable properties were achieved with forging reductions (of the 72" width dimension of the ingot) to 24, 20, 16

and 12 inches, representing, respectively, 66%, 71%, 78% and 83%. Since the final plate thicknesses were substantially the same, the corresponding rolling reductions were approximately 79%, 75%, 69% and 60%. In each case the overall reduction was about 93 Photomicrographs showed little difference in the structure of -inch plate (T81 temper) rolled from any section of the step forged billet.

The ratio of forging reduction to rolling reduction in these instances ranged from about 2.4:1 to about 8.3:1.

Example 4 Results similar to those described in the preceding eX- amples have been obtained with other alloys, the following situations being representative:

(a) An ingot of 2024 alloy measuring approximately 16 x 52 inches in cross-section was homogenized at 880'- 930 F., and subsequently forged to reduce the 52-inch dimension to about 12 inches. Further reduction of that dimension was effected by rolling the forged billet into a plate 5 inches in thickness.

(b) An ingot of 7079 alloy measuring approximately 26 x 72 inches in cross-section was homogenized at 850- 950 F., and sections of the ingot were subsequently forged to reduce the 72-inch dimension to 17 inches, in one case, and also to 24 inches. Plate 4 and 6 inches in thickness was rolled from each size of forged billet.

While present preferred embodiments of the invention have been illustrated and described, it will be apparent that the invention may be otherwise variously embodied and practiced within the scope of the following claims.

What is claimed is:

1. The method of producing wrought aluminum alloy plate having .a thickness of at least about 3 inches, comprising the steps of providing an aluminum alloy ingot having a width greater than its thickness, homogenizing the ingot by a heat treatment, hot forging the ingot to effect a reduction of at least 25% in its width dimension and form .a billet already worked substantially in the short transverse direction, and rolling said billet into a plate, the combination of said forging and rolling steps producing a wrought structure extending substantially throughout the resultant plate.

2. The method of claim 1 wherein the ratio of forging reduction to rolling reduction in a direction corresponding to the short transverse direction of said plate is in the range from about 2.421 to about 8.321.

3. The method of claim 1, in which the ingot is retated 90 after an initial forging reduction of its width, and is thereafter subjected to an additional forging operation to effect a reduction of its thickness prior to rolling the forged billet into a plate.

4. The method of producing a high-strength wrought aluminum alloy structure of substantial thickness, comprising the steps of: providing a cast ingot of said alloy having a thickness of about 12 to 24 inches and a width at least twice its thickness, homogenizing the ingot by a heat treatment, hot forging the ingot to effect a reduction of at least 25 in its width dimension under conditions permitting expansion of its thickness, thereby providing a preforged billet already worked substantially in the short transverse direction, and hot rolling said billet to effect an additional reduction in said width dimension amounting to at least about 3:1.

5. The method of claim 4, in which said forging step effects a total reduction of about to about in the Width of the ingot.

References Cited UNITED STATES PATENTS 1,178,813 4/1916 Lloyd. 1,408,330 2/1922 Witler. 1,483,451 2/1924 Kenney. 1,632,533 6/ 1927 Brauchler. 2,285,308 6/1942 Speckt. 2,465,792 3/1949 Davis.

CHARLIE T. MOON, Primary Examiner.

JOHN F. CAMPBELL, Examiner.

R. F. DROPKIN, P. M. COHEN, Assistant Examiners. 

1. THE METHOD OF PRODUCING WROUGHT ALUMINUM ALLOY PLATE HAVING A THICKNESS OF AT LEAST ABOUT 3 INCHES, COMPRISING THE STEPS OF PROVIDING AN ALUMINUM ALLOY INGOT HAVING A WIDTH GREATER THAN ITS THICKNESS, HOMOGENIZING THE INGOT BY A HEAT TREATMENT, HOT FORGING THE INGOT TO EFFECT A REDUCTION OF AT LEAST 25% IN ITS WIDTH DIMENSION AND FORM A BILLET ALREADY WORKED SUBSTANTIALLY IN THE SHORT TRANSVERSE DIRECTION, AND ROLLING SAID BILLET INTO A PLATE, THE COMBINATION OF SAID FORGING AND ROLLING STEPS PRODUCING A WROUGHT STRUCTURE EXTENDING SUBSTANTIALLY THROUGHOUT THE RESULTANT PLATE. 